stumped on a dying issue

1965 coronet.
5.9 magnum out of a 2000 durango.
Megasquirt 2 running the stock efi, with a mod to the distributor so it doesn't need a crank sensor.
It has a shutter wheel to give it timing.

After driving it for a bit after it gets up to operating temp it starts to stumble, and run rough. eventually dying.
It will restart once or twice, also running rough and then won't run again for 15 to 20 min or so. Then it will restart like nothing happened.

I have replaced the coil, the surge tank fuel pump.
I rechecked the MS box for the jumpers I put in, in case they might have overheated and melted the solder.
one of the wires I used as a jumper had some corrosion on it and I replaced it with a solid wire jumper.
but all the solder joints were solid when I took it apart.

The only things left might be temp sensors and the distributor sensor.

feets suggested logging data from the megasquirt, but I am not sure what I should be seeing to decide what sensor died.
RPM followed what I felt, and AFR went to 10, which I think means the injectors were still firing.
Is there some specific test I should try?
how would I tell what isn't working when it is dead?
I mean I am pretty sure it is spark now, but how do I find the part causing it?

What are you using for ignition? With the exception of starting again after cooling down, I had an MSD 6AL fail the same way.

Kevin

Had a coil fail like that. Eventually it got tot eh point where it no longer started up at all and that's what it took to figure it out for me, because invariably it'd die when I had no T/S tools handy,

it is the stock coil which I replaced already from the 5.9.
It is being driven by the mega squirt.

I suppose the replacement could be bad too, but seems unlikely since the symptoms are the same after the replacement.

I have been trying to think of what else could affect it.

I have put this car together with independent systems to prevent cascading failures.

The only thing the engine harness gets from the old car harness is the key on power in start and run.
I tied the run and start wires together under the hood to a relay and that gives 12 volts to the MS system.

everything else is just the engine harness.

power is new wiring independent of the old car harness.

I hate throwing parts, but other than temp sensors, the only thing left is the distributor pickup or the computer itself.

Go get a can of "air" like you clean keyboards with. Get things hot so that the engine dies, use the "air" to cool things down one at a time till it fires. That's how you can find stuff that fails hot but not cold (yet).

now that is an interesting test.
Thanks for the idea.

I find spraying with the can upside down works best.

Distributor sensor could certainly be it, it could also be it's air gap. How much gap is there from the sensor to the pickup? If it's a VR sensor, it could also be very susceptible to noise/RFI. Instantaneous and wrong high RPM can demand high fueling, it'll show up on a log, but likely not a tach.

You can probably do a tooth trace/high fidelity log and watch each crank tooth, if you see the crank signal just drop out, that'll tell you something for sure.

- What's the rpm log look like?

- Hitting 93kPa with a maximum TPS of 16% seems a little suspect. if the MAP signal isn't accurate, it jumping to 93kpa will just dump fuel [also seeing low/rich AFR]

- Try cutting down on the number of common data names you are using per trace in megalog viewer, PW x PW x VE1 x VE2 isn't very useful. I would scale the TPS chart to show 0-100%, it looks like the scale is showing ~0-20%, which makes 16% look very high. Small tweaks in MLV will help your data start to show a bit clearer story.

- I'd like to see your MAT trace and MAT fuel correction as well. There is a MAT correction curve that, if wrong, can dump a good amount of fuel on top of the base fuel table. There is on my MS3, not sure about MS2.

I don't know how much gap there is. It is a shutter wheel, so it passes through the sensor.
that hasn't changed as far as I know. In that if that were the issue, I would expect it to be all the time. ?

I was just barely on the throttle, so pretty low rpm, and it started to chug like that.

It is the same logging software, I just have to figure out how to set it to show what I need.
or maybe I have to pay for the registered version to get all the bells and whistles.
All I did was start logging, I didn't see any settings for what to log, so maybe all the data is there, I just can't see it.

I haven't messed with any of the curves or any of the computer stuff since I got it running a few years back.
I switched from the prototype painless setup when it started blowing fuses.

Wouldn't a drop in the pickup also stop firing the injectors? or since they are batch, there is enough to keep it running?

and wow canned air is expensive for what it is. lol.

What does your exhaust look like. We had a problem with a 5.2 when the cobbled up exhaust came apart about a foot behind the downstream O2 sensor. It ran, but not well. I don't remember if it ran ok in open loop or not, though.

It sounds like a thermal issue. First suspect coil, second suspect distributor pickup, third suspect ECM. If I was a betting man, I'd go with the distributor pickup.

exhaust is good. no leaks. had a whole new one made for it after I dropped the 5.9 in.

yeah, I think that is the only thing left it can be is the pickup, but I hate to throw more parts at it till I can "prove" something.

I see I can get a "new" distributor for 70 bucks vs 24 for just the pickup. If I go that route, I might do that instead of just a part.

IIRC, that has the Ford 5.0 distributor pickup? I'd look at that for sure. Another friend had the same symptoms, and a new distributor (with a new pickup) fixed it.

no, mine is the stock pickup for a 2000 5.9.
they added a shutter wheel to give it a different signal.

Thanks though, it makes it more likely.
I got some canned air and will give it a test soon.

ran the canned air test.
I guess it must be the distributor.

it died, I got it to fire again, then it died and finally it wouldn't restart. I iced down the distributor and it fired right up.

Just debating on where to buy it from now, if I have to deal with the warranty.